The present invention relates to a circuit arrangement for electrical machines and deals in particular with starting circuits for starter-generators to be used in a motor vehicle.
Conventionally in motor vehicles two electrical machines are used namely a generator which is driven from the vehicle and produces electrical energy for supply of a vehicle electrical system consumer and for charging the battery, and furthermore a starter that operates as an electric motor and in the case of starting the motor brings the vehicle to a required minimum rotary speed. Also, such systems are known which have a single electrical machine designed as a starter-generator and operating both for starting the motor and for producing the electrical energy.
Such starter generators are for example flywheel starter-generators or crankshaft starter-generators which are directly in connection with the crankshaft of the motor. The utilized starter generators are three phase current machines which are connected with the vehicle battery through a power electronic system which includes a pulse inverter bridge. The control of the pulse inverter or pulse converter is performed by a current supply itself or by an associated control electronic system. When the electrical machine is for example a permanently excited synchronous machine, then when the machine is rotated a voltage is produced regardless of whether the electronic system is activated or not. With a correspondingly high rotary speed of the synchronous machine it leads to exceeding of the allowable voltage, and there is a danger that the electronic system of the starter generator as well as the vehicle electronic system can be destroyed.
A vehicle electrical system with a starter generator as well as a method for regulating such a starter generator which is connected with the vehicle battery through a pulse inverter bridge is disclosed for example in the German patent document DE 197 33 212 A1. In such a known system, the pulse inverter elements are controlled by a regulating electronic system in a suitable manner, which in the generator operation guarantees an optimal generator regulation and thereby a maximum generation of electrical power. Simultaneously with suitable control of the pulse inverter elements its guaranteed that during the starting of the electrical machine electrical energy can be taken from the battery and thereby operate as an electric motor and the vehicle motor can be accelerated to the starting rotary speed.
Since such known systems deal with the optimal regulation of the generator operating machine in normal operation, no provisions for starting are made and no special starting circuits for the starter generator are provided.
Control devices for starters of internal combustion engines are known in principle and are for example described in the German patent document DE-P 10 034 794.7. This known control devices for a starter include also circuits in which MOSFET-switching transistors can be used, via which for example the holding winding of the starter relay is controlled. One of such MOSSFET transistors is a starting switch. The control of the switching transistors is performed by an electrical start control, which in turn is connected through an interface with the motor control device and obtains from it informations, for example rotary speed informations. The MOSSFET transistor which operates as a starting switch is associated in accordance with one of the examples with a charge pump
Accordingly, it is an object of the present invention to provide a circuit arrangement for electrical machines which is a further improvement of the existing arrangements.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a circuit arrangement for an electrical machine which is connected with at least one phase terminal of the electrical machine, the circuit arrangement comprising at least one passive charge pump which is connectable directly with phase windings of the electrical machine; and has another terminal connected through further electronic means with an input/output, at which a switching on/switching off signal for a current supply is produced.
When the circuit arrangement for electrical machines is designed in accordance with the present invention, it has the advantage that a more reliable start for the current supply of the control electronic system of the electrical machine can be performed.
The associated starting circuit is formed especially simply and can recognize in a simple manner the rotatable machine. Furthermore, the starting circuit, in an especially advantageous manner, is in the position in which it activates the current supply and thereby the complete control electronic system, in particular exactly after the recognized beginning of rotation. This is also possible in deactivated condition of the electronic system.
In a further especially advantageous manner, with the activated control electronic system, via the use of corresponding features, the output voltage of the electrical machine which operates as a generator can be regulated. It is especially advantageous that low circuit expenses are needed, characterized by only four passive components. Furthermore, in a especially advantageous manner no closed-circuit current flows for supplying the charge lamp and a reliable detection of a rotatable machine is possible also with deactivated control electronic system.
Additional advantages are provided when a circuit arrangement includes a passive charge lamp, which is connected with the phase terminal of any semi-bridge of the converter bridge.
In accordance with a further embodiment of the present invention, the passive charge lamp advantageously can be formed only with two capacitors and two diodes.
An advantageous use of the inventive circuit arrangement is possible for starter-generators, in particular crankshaft starter-generators for vehicles.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operational, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.